Update dependency django-anymail to v10.3

[renovate]

This PR contains the following updates:

Package	Change	Age	Adoption	Passing	Confidence
django-anymail (changelog)	10.2 -> 10.3

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Release Notes

anymail/django-anymail (django-anymail)

v10.3

Compare Source

2024-03-12

Features

* **Brevo:** Add support for batch sending
  (`docs <https://anymail.dev/en/stable/esps/brevo/#batch-sending-merge-and-esp-templates>`__).

* **Resend:** Add support for batch sending
  (`docs <https://anymail.dev/en/stable/esps/resend/#batch-sending-merge-and-esp-templates>`__).

* **Unisender Go:** Newly supported ESP
  (`docs <https://anymail.dev/en/stable/esps/unisender_go/>`__).
  (Thanks to `@Arondit`_ for the implementation.)

Fixes
~~~~~

* **Mailgun:** Avoid an error when Mailgun posts null delivery-status
  to the event tracking webhook. (Thanks to `@izimobil`_ for the fix.)

Deprecations

• Brevo (SendinBlue): Rename "SendinBlue" to "Brevo" throughout
  Anymail's code, reflecting their rebranding.
  This affects the email backend path, settings names, and webhook URLs.
  The old names will continue to work for now, but are deprecated. See
  Updating code from SendinBlue to Brevo <https://anymail.dev/en/stable/esps/brevo/#brevo-rename>__
  for details.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.81%. Comparing base (d409202) to head (4e80fd0).

Additional details and impacted files

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  Coverage   74.81%   74.81%           
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  Files         245      245           
  Lines       11204    11204           
  Branches     1947     1947           
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  Hits         8382     8382           
  Misses       2648     2648           
  Partials      174      174           

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